Congenital cytomegalovirus (CMV) infection is the most common non-genetic cause of sensorineural hearing loss (SNHL) in children, accounting for between 20 and 60% of all SNHL. It is estimated that at least 8000 infants born annually in the US will have congenital CMV-induced SNHL, with a significant proportion of these children exhibiting delayed onset and progressive deterioration of hearing after the newborn period. Currently, little is known about the mechanism underlying CMV-induced birth defects. Since in utero CMV infection causes SNHL whereas postnatal infection does not, we postulate that CMV-induced cochlear malformations are caused by viral-induced dysregulation of multiple host (embryonic) cell signaling pathways essential for normal cochlear morphogenesis and that the severity of dysmorphogenesis is time-dependent. We have recently developed a novel mouse embryonic organ culture model of CMV-induced cochlear malformations and demonstrate that active CMV infection of embryonic mouse cochlears in vitro induces severely abnormal cochlear phenotypes and labyrinthitis. Our preliminary results indicate that this novel embryonic mouse cochlear culture model mimics the pathology seen in children with congenital CMV infection. Our objective is to initiate delineation of the molecular pathology of the CMV-induced cochlear abnormalities using our novel in vitro embryonic mouse organ culture model of CMV-induced cochlear malformation. Long-term, our goal is to identify the molecular mechanisms underlying CMV-induced cochlear dysmorphogenesis and identify key cellular targets against which new cochlear- specific, postnatal therapies can be directed. We have designed a series of interrelated experiments to address three Specific Aims. Aim 1: Characterize mCMV-induced changes in embryonic cochlear morphology, histodifferentiation and cell proliferation in vitro. Aim 2: Determine mCMV-induced differences in the gene expression of a focused set of "cochlea-related" signaling molecules. Aim 3: Determine time-dependent differences in the molecular pathology of mCMV-induced cochlear abnormalities. The results of our initial studies will provide a detailed molecular phenotype of CMV-induced cochlear pathology. An informed and rational framework will emerge within which future mechanistic studies may be planned and proposed to identify which cellular signaling pathways are functionally essential for CMV-induced cochlear pathogenesis, and likely putative targets against which new therapies can be directed will emerge. Our in vitro model also has the added translational value of providing a system for initial screening of all classes of new candidate, cochlear-targeted, postnatal anti-CMV drugs, including antivirals. This line of investigation is clinically critical because the prevalence of CMV-induced SNHL is considerable, present antiviral therapies are teratogenic in themselves, and long-term use of current antiviral drugs by infected children present serious safety concerns. PUBLIC HEALTH RELEVANCE: Congenital cytomegalovirus (CMV) infection is the most common non-genetic cause of sensorineural hearing loss (SNHL) in children, accounting for between 20 and 60% of all SNHL. It is estimated that at least 8000 infants born annually in the US will have congenital CMV-induced SNHL. Since little is presently known about the mechanisms underlying CMV-induced abnormalitites, the objective of this project is to initiate delineation of the molecular pathology of the CMV-induced cochlear abnormalities. The ultimate goal of this research is to identify the molecular mechanisms underlying CMV-induced cochlear dysmorphogenesis and identify cellular targets against which new cochlear-specific, postnatal therapies can be directed to ameliorate SNHL due to congenital CMV infection. In addition, our in vitro model has the added translational value of providing an efficient model system for initial screening of all classes of new tissue-targeted drugs for their ability to preclude CMV-induced pathology. This is clinically important because the prevalence of CMV-induced SNHL is considerable, present antiviral therapies are teratogenic in themselves, and long-term use of current antiviral drugs by infected children present serious safety concerns.